feat: browser_choose_file (#52)

Resolves https://github.com/microsoft/playwright-mcp/issues/31.

Prompt used for testing: 
```
upload test.txt to dropbox
```

This won't work for asynchronously opened filechoosers, but let's start
with the synchronous variant. I also tested with including the file
chooser open state in the snapshot, but that didn't give better results.

I also tested with OneDrive and WeTransfer, but somehow our ARIA
snapshots for those pages are missing some elements that are crucial to
locate the upload buttons.

src/tools/common.ts

@@ -156,3 +156,21 @@ export const close: Tool = {
     };
   },
 };
+
+const chooseFileSchema = z.object({
+  paths: z.array(z.string()).describe('The absolute paths to the files to upload. Can be a single file or multiple files.'),
+});
+
+export const chooseFile: ToolFactory = snapshot => ({
+  schema: {
+    name: 'browser_choose_file',
+    description: 'Choose one or multiple files to upload',
+    inputSchema: zodToJsonSchema(chooseFileSchema),
+  },
+  handle: async (context, params) => {
+    const validatedParams = chooseFileSchema.parse(params);
+    return await runAndWait(context, `Chose files ${validatedParams.paths.join(', ')}`, async () => {
+      await context.submitFileChooser(validatedParams.paths);
+    }, snapshot);
+  },
+});